July is a busy time in the greenhouse, not just for maintenance but sowing and harvesting, too.
Maintain a regular regime of feeding and watering with tepid water. Find out if your containerised plants need watering by sticking your finger into the surface of the compost, if your finger is free of compost particles when you pull it out then the plant needs watering. It’s also helpful to learn how to judge this by the weight of the pot with wet and dry compost. When watering, give plants a thorough soak; a light sprinkle will only encourage roots to the surface where they are more susceptible to drought.
Maintain humidity by damping down the floor of the greenhouse, I also mist cucumbers with a hand sprayer twice a day to ensure humidity is maintained around the underside of the leaves this reduces problems with red spider (or two spotted) mite.
Check plants regularly for signs of whitefly, leafhopper, glasshouse red spider mite, mealybugs and scale insects and treat them with biological controls or environmentally friendly sprays. Keep the glasshouse free of fallen leaves, flowers and other plant debris to prevent the spread of diseases.
Remove the side shoots from tomatoes as early as possible. Tie in and pinch out the main stems of tomato plants once they reach the top of the support, so all of the energies are channelled into ripening of existing tomatoes. Harvest crops regularly and train cucumbers and melons onto nets and frames; repot chillies, bell peppers and aubergines until they are in 23cm pots of peat substitute compost. Tie sweet peppers and aubergines to supporting canes if needed.
The following can be sown in July: Basil, Calabrese, Chinese cabbage, Winter purslane, (Claytonia), Chervil, Coriander and Dill, French beans (climbing and dwarf) Lettuce, Florence fennel, Oriental greens like Pak Choi, Parsley, chard, endive, chicory, beetroot.
Feed citrus with specialist food and continue training climbing plants like Gloriosa superba ‘Rothschildiana’ in a spiral around a tripod of canes, tying in as needed. Keep the pot at the back of the greenhouse away from the doorway where humidity is higher. I am thrilled that mine has just produced its first flower.
The lack of light and cool temperatures have slowed growth in my greenhouse, this year. Sweet peppers and aubergines are very slow to side shoot. If temperatures are unseasonally low, ventilate using the windows rather than opening the door which causes a draught. One of the positives is that as soon as light and temperature levels increase tender plants burst into rapid grown and will soon flower and fruit.
From mid-July take semi-ripe cuttings from shrubs like ‘Star Jasmine’, Camellia, Ceanothus, Choisya, Cistus, Convolvulus cneorum, Fatsia, Mahonia and Viburnum. Cuttings taken in summer, rarely need heated propagator. Keep the compost moist until they are well rooted and shade them from sunshine in hot weather. Remove any dead or diseased cuttings and leaves that fall. Once the cuttings have rooted, they will need ‘hardening off’ for two to three weeks before potting on or planting out. Happy gardening, Matt